#方法二：使用切片的方法实现
phrase = "Don't panic!"
plist = list(phrase)  # list()可以将 str to(转) list
print(phrase)
print(plist)

on_str = ''.join(plist[1:3])
print(on_str)
new_phrase =on_str+''.join(plist[5]+plist[4]+plist[7]+plist[6])
print(plist)
print(phrase)